1997 Pontiac Grand Am oscillating idle in park when engine

1997 PONTIAC GRAND AM
60,000 MILES • 6 CYL • FWD • AUTOMATIC
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DIESEL250
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Hello, Pontiac Grand am 1997 V6 SFI 3.1L has an intermittent problem with idle. Sometimes when warm engine is started in P idle will jump up and down very fast from about 300RPM-1200RPM only when engine is warmed up and only in Park. As soon as transmission is shifted form P to D no problems at all. No vacuum leaks, no DTC. TB, IAC EGR are all good and clean. Please help
Apr 2, 2009 at 2:16 PM
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MMPRINCE4000
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Check for vacuum leaks, it may be that when shifting into drive the engine moves enough to stop the leak.
Apr 3, 2009 at 8:00 AM